Systems and methods for using a speaker as a microphone in a mobile device

ABSTRACT

In accordance with methods and systems of the present disclosure, a mobile device may include an enclosure adapted such that the enclosure is readily transported by a user of the mobile device, a speaker associated with the enclosure for generating sound, and a controller within the enclosure, communicatively coupled to the speaker. The controller may be configured to receive a signal from the speaker, the signal induced at least in part by sound incident on the speaker other than sound generated by the speaker and process the signal.

RELATED APPLICATION

The present disclosure claims priority to U.S. patent application Ser.No. 13/915,767, filed Jun. 12, 2013, issuing as U.S. Pat. No. 9,008,344on Apr. 14, 2015, and U.S. Provisional Patent Application Ser. No.61/782,388, filed Mar. 14, 2013, both of which are incorporated byreference herein in their entirety.

FIELD OF DISCLOSURE

The present disclosure relates in general to a mobile device, and moreparticularly, to using a speaker as a microphone in a mobile device inorder to potentially improve power performance and/or audio performanceof the mobile device.

BACKGROUND

Battery life in mobile devices (e.g., smart phones, tablets, handheldcomputers, other portable devices, etc.) is often a key designconstraint. Accordingly, mobile devices are capable of being placed in alower-power state or “sleep mode.” In this low-power state, generallyonly minimal circuitry is active, such minimal circuitry includingcomponents necessary to sense stimulus for activating higher-power modesof operations. Typically, one of the components remaining active is oneor more capacitive microphones, in order to sense for voice activationcommands for activating a higher-power state. Often, these microphonesconsume significant amounts of power, thus reducing battery life ofmobile devices.

Another shortcoming of capacitive microphones typically used in mobiledevices are that they are typically suited for receiving low-volumesounds with a limited frequency range. However, it may be desirable torecord loud sounds, such as a rock concert, which are above the volumerange for which most capacitive microphones used in mobile devices aresuited. Amplifier circuitry and bias electronics used to amplifyelectric signals transduced by sound received by such microphonestypically draw significant amounts of power, and adapting such circuitryto increase the audio performance of microphones would likely increasepower consumption and component cost. Some mobile device manufacturershave overcome this shortcoming by including two capacitive microphones:one adapted for low-volume sound, and one adapted for high-volume sound.However, such a solution may increase cost.

SUMMARY

In accordance with the teachings of the present disclosure, thedisadvantages and problems associated with performance of microphones ina mobile device may be reduced or eliminated.

In accordance with embodiments of the present disclosure, a mobiledevice may include an enclosure adapted such that the enclosure isreadily transported by a user of the mobile device, a speaker associatedwith the enclosure for generating sound, and a controller within theenclosure, communicatively coupled to the speaker. The controller may beconfigured to receive a signal from the speaker, the signal induced atleast in part by sound incident on the speaker other than soundgenerated by the speaker and process the signal.

In accordance with these and other embodiments of the presentdisclosure, a method may include generating, by a speaker associatedwith an enclosure adapted such that the enclosure is readily transportedby a user of the mobile device, a signal, the signal induced at least inpart by sound incident on the speaker other than sound generated by thespeaker and processing the signal.

In accordance with these and other embodiments of the presentdisclosure, a mobile device may include an enclosure adapted such thatthe enclosure is readily transported by a user of the mobile device, afirst speaker associated with the enclosure for generating sound, asecond speaker associated with the enclosure for generating sound, and acontroller within the enclosure, communicatively coupled to the speaker.The controller may be configured to receive a first signal from thefirst speaker, the first signal induced at least in part by soundincident on the first speaker other than sound generated by the firstspeaker, receive a second signal from the first speaker, the secondsignal induced at least in part by sound incident on the second speakerother than sound generated by the second speaker, process at least oneof the first signal and the second signal to determine at least onecharacteristic of sound incident on the mobile device, select one of thefirst speaker and the second speaker as a signal source for incidentsound based on at least one of the volume level and the frequency; andselect the other one of the first speaker and the second speaker togenerate sound based on at least one of the volume level and thefrequency.

In accordance with these and other embodiments of the presentdisclosure, a method may include generating, by a first speakerassociated with an enclosure adapted such that the enclosure is readilytransported by a user of the mobile device, a first signal, the firstsignal induced at least in part by sound incident on the first speakerother than sound generated by the first speaker. The method may alsoinclude generating, by a second speaker associated with the enclosure, asecond signal, the second signal induced at least in part by soundincident on the second speaker other than sound generated by the secondspeaker. The method may additionally include processing at least one ofthe first signal and the second signal to determine at least onecharacteristic of sound incident on the mobile device. The method mayfurther include selecting one of the first speaker and the secondspeaker as a signal source for incident sound based on at least one ofthe volume level and the frequency. The method may also includeselecting the other one of the first speaker and the second speaker togenerate sound based on at least one of the volume level and thefrequency.

Technical advantages of the present disclosure may be readily apparentto one having ordinary skill in the art from the figures, descriptionand claims included herein. The objects and advantages of theembodiments will be realized and achieved at least by the elements,features, and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description andthe following detailed description are examples and explanatory and arenot restrictive of the claims set forth in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 illustrates a block diagram of an example mobile device, inaccordance with embodiments of the present disclosure;

FIG. 2 illustrates a flow chart of an example method for using a speakeras a microphone in order to detect audio stimulus for waking a mobiledevice from a low-power state, in accordance with embodiments of thepresent disclosure;

FIG. 3 illustrates a flow chart of an example method for using a speakeras a microphone at higher volume levels not suitable for reception by acapacitive microphone, in accordance with embodiments of the presentdisclosure;

FIG. 4 illustrates a flow chart of an example method for simultaneouslyusing a speaker as a speaker and a microphone such that the speaker maysimultaneously emit sound while capturing sound, in accordance withembodiments of the present disclosure; and

FIG. 5 illustrates a flow chart of an example method for selectivelyenabling speakers for transmitting sound or receiving sound, inaccordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a block diagram of an example mobile device 102, inaccordance with embodiments of the present disclosure. As shown in FIG.1, mobile device 102 comprises an enclosure 101, a controller 103, amemory 104, a user interface 105, a microphone 106, a radiotransmitter/receiver 108, and one or more speakers 110.

Enclosure 101 comprises any suitable housing, casing, or other enclosurefor housing the various components of mobile device 102. Enclosure 101may be constructed from plastic, metal, and/or any other suitablematerials. In addition, enclosure 101 may be adapted (e.g., sized andshaped) such that mobile device 102 is readily transported on a personof a user of mobile device 102. Accordingly, mobile device 102 includesbut is not limited to a smart phone, a tablet computing device, ahandheld computing device, a personal digital assistant, a notebookcomputer, or any other device that may be readily transported on aperson of a user of mobile device 102.

Controller 103 is housed within enclosure 101 and includes any system,device, or apparatus configured to interpret and/or execute programinstructions and/or process data, and may include, without limitation amicroprocessor, microcontroller, digital signal processor (DSP),application specific integrated circuit (ASIC), or any other digital oranalog circuitry configured to interpret and/or execute programinstructions and/or process data. In some embodiments, controller 103interprets and/or executes program instructions and/or processes datastored in memory 104 and/or other computer-readable media accessible tocontroller 103.

Memory 104 may be housed within enclosure 101, may be communicativelycoupled to controller 103, and includes any system, device, or apparatusconfigured to retain program instructions and/or data for a period oftime (e.g., computer-readable media). Memory 104 may include randomaccess memory (RAM), electrically erasable programmable read-only memory(EEPROM), a Personal Computer Memory Card International Association(PCMCIA) card, flash memory, magnetic storage, opto-magnetic storage, orany suitable selection and/or array of volatile or non-volatile memorythat retains data after power to mobile device 102 is turned off.

User interface 105 may be housed at least partially within enclosure101, may be communicatively coupled to controller 103, and comprises anyinstrumentality or aggregation of instrumentalities by which a user mayinteract with user mobile device 102. For example, user interface 105may permit a user to input data and/or instructions into user mobiledevice 102 (e.g., via a keypad and/or touch screen), and/or otherwisemanipulate mobile device 102 and its associated components. Userinterface 105 may also permit mobile device 102 to communicate data to auser, e.g., by way of a display device.

Capacitive microphone 106 may be housed at least partially withinenclosure 101, may be communicatively coupled to controller 103, andcomprises any system, device, or apparatus configured to convert soundincident at microphone 106 to an electrical signal that may be processedby controller 103, wherein such sound is converted to an electricalsignal using a diaphragm or membrane having an electrical capacitancethat varies as based on sonic vibrations received at the diaphragm ormembrane. Capacitive microphone 106 may include an electrostaticmicrophone, a condenser microphone, an electret microphone, amicroelectomechanical systems (MEMs) microphone, or any other suitablecapacitive microphone.

Radio transmitter/receiver 108 may be housed within enclosure 101, maybe communicatively coupled to controller 103, and includes any system,device, or apparatus configured to, with the aid of an antenna, generateand transmit radio-frequency signals as well as receive radio-frequencysignals and convert the information carried by such received signalsinto a form usable by controller 103. Radio transmitter/receiver 108 maybe configured to transmit and/or receive various types ofradio-frequency signals, including without limitation, cellularcommunications (e.g., 2G, 3G, 4G, LTE, etc.), short-range wirelesscommunications (e.g., BLUETOOTH), commercial radio signals, televisionsignals, satellite radio signals (e.g., GPS), Wireless Fidelity, etc.

A speaker 110 may be housed at least partially within enclosure 101 ormay be external to enclosure 101, may be communicatively coupled tocontroller 103, and may comprise any system, device, or apparatusconfigured to produce sound in response to electrical audio signalinput. In some embodiments, a speaker may comprise a dynamicloudspeaker, which employs a lightweight diaphragm mechanically coupledto a rigid frame via a flexible suspension that constrains a voice coilto move axially through a cylindrical magnetic gap. When an electricalsignal is applied to the voice coil, a magnetic field is created by theelectric current in the voice coil, making it a variable electromagnet.The coil and the driver's magnetic system interact, generating amechanical force that causes the coil (and thus, the attached cone) tomove back and forth, thereby reproducing sound under the control of theapplied electrical signal coming from the amplifier.

In embodiments in which mobile device 102 includes a plurality ofspeakers 110, such speakers 110 may serve different functions. Forexample, in some embodiments, a first speaker 110 may play ringtonesand/or other alerts while a second speaker 110 may play voice data(e.g., voice data received by radio transmitter/receiver 108 fromanother party to a phone call between such party and a user of mobiledevice 102). As another example, in some embodiments, a first speaker110 may play voice data in a “speakerphone” mode of mobile device 102while a second speaker 110 may place voice data when the speakerphonemode is disabled.

Although specific example components are depicted above in FIG. 1 asbeing integral to mobile device 102 (e.g., controller 103, memory 104,user interface 105, microphone 106, radio transmitter/receiver 108,speakers(s) 110), a mobile device 102 in accordance with this disclosuremay comprise one or more components not specifically enumerated above.

In accordance with embodiments of the present disclosure, one or more ofspeakers 110 may also be employed as a microphone. To illustrate, soundincident on a cone or other sound producing component of a speaker 110may cause motion in such cone, thus causing motion of the voice coil ofsuch speaker 110, which induces a voltage on the voice coil which may besensed and transmitted to controller 103 and/or other circuitry forprocessing, effectively operating as a microphone. Sound detected by aspeaker 110 used as a microphone may be used for many purposes, asdescribed below.

For example, in some embodiments a speaker 110 may be used as amicrophone to sense voice commands and/or other audio stimulus for“waking up” mobile device 102 from a low-power state and transitioningit to a higher-power state. In such embodiments, when mobile device 102is in a low-power state, a speaker 110 may communicate electronicsignals to controller 103 for processing. Controller 103 may processsuch signals and determine if such signals correspond to a voice commandand/or other stimulus for transitioning mobile device 102 to ahigher-power state. If controller 103 determines that such signalscorrespond to a voice command and/or other stimulus for transitioningmobile device 102 to a higher-power state, controller 103 may activateone or more components of mobile device 102 that may have beendeactivated in the low-power state (e.g., capacitive microphone 106,user interface 105).

In some instances, a speaker 110 may be used as a microphone for soundpressure levels or volumes above a certain level, such as the recordingof a live concert, for example. In such higher sound levels, a speaker110 may have a more reliable signal response to sound as compared withcapacitive microphone 106. When using a speaker 110 as a microphone,controller 103 and/or other components of mobile device 102 may performfrequency equalization, as the frequency response of a speaker 110employed as a microphone may be different than capacitive microphone106. Such frequency equalization may be accomplished using filters(e.g., a filter bank) as is known in the art. In particular embodiments,such filtering and frequency equalization may be adaptive, with anadaptive filtering algorithm performed by controller 103 during periodsof time in which both capacitive microphone 106 is active (but notoverloaded by the incident volume of sound) and a speaker 110 is used asa microphone. Once the frequency response is equalized, controller 103may smoothly transition between the signals received from capacitivemicrophone 106 and speaker 110 by cross-fading between the two.

In these and other embodiments, controller 103 may process signalsreceived from capacitive microphone 106 and one or more speakers 110employed as microphones in order to perform beamforming or spatialfiltering, which is a signal processing technique for directional signalreception. Controller 103 may perform beamforming by combining elementsin a phased array in such a way that signals at particular anglesexperience constructive interference while others experience destructiveinterference. Beamforming may be in order to achieve spatial selectivityof sounds incident at mobile device 102.

In these and other embodiments, a speaker 110 may be used as amicrophone in those instances in which it is not otherwise beingemployed to emit sound. For example, when mobile device 102 is in alow-power state, a speaker 110 may not emit sound and thus may beemployed as a microphone (e.g., to assist in waking mobile device 102from the low-power state in response to voice activation commands, asdescribed above). As another example, when mobile device 102 is in aspeakerphone mode, a speaker 110 typically used for playing voice datato a user when mobile device 102 is not in a speakerphone mode (e.g., aspeaker 110 the user typically holds to his or her ear during atelephonic conversation) may be deactivated from emitting sound and insuch instance may be employed as a microphone.

However, in other embodiments, a speaker 110 may be used simultaneouslyas a speaker and a microphone, such that a speaker 110 maysimultaneously emit sound while capturing sound. In such embodiments, acone and voice coil of a speaker 110 may vibrate both in response to avoltage signal applied to the voice coil and other sound incident uponspeaker 110. Controller 103 may determine a voltage present on the voicecoil, which will include the sum of two voltages: a voltage transmitted(e.g., by controller 103) for generating sound from the speaker 110 anda voltage induced by external sound incident on the speaker 110. Byperforming signal processing, controller 103 may subtract the voltageattributable to generating sound from the total voltage present on thevoice coil, with the remaining voltage being attributable to theexternal sound incident on the speaker 110.

In these and other embodiments, a speaker 110 may be used as amicrophone in order to extend a bass response of mobile device 102beyond that of capacitive microphone 106. Typical capacitive microphoneshave limited frequency response, especially at low frequencies. However,when used as a microphone, a speaker 110 may have a better low-frequencyresponse as compared to capacitive microphones typically employed inmobile devices. Thus, controller 103 may filter and sum signals fromcapacitive microphone 106 and one or more speakers 110 to provide agreater frequency response for reception of sound than might beavailable from capacitive microphone 106 alone.

In these and other embodiments, mobile device 102 may include at leasttwo speakers 110 which may be selectively used to transmit sound or as amicrophone. In such embodiments, each speaker 110 may be optimized forperformance at a particular volume level range and/or frequency range,and controller 103 may select which speaker(s) 110 to use fortransmission of sound and which speaker(s) 110 to use for reception ofsound based on detected volume level and/or frequency range.

FIG. 2 illustrates a flow chart of an example method 200 for using aspeaker 110 as a microphone in order to detect audio stimulus for wakingmobile device 102 from a low-power state, in accordance with embodimentsof the present disclosure. According to one embodiment, method 200begins at step 202. As noted above, teachings of the present disclosureare implemented in a variety of configurations of mobile device 102. Assuch, the preferred initialization point for method 200 and the order ofthe steps comprising method 200 may depend on the implementation chosen.

At step 202, a speaker 110 may be disabled from generating soundresponsive to mobile device 102 entering a low-power state. At step 204,the speaker 110 may, responsive to sound incident upon speaker 110,transmit a voltage signal induced in the speaker 110 by the incidentsound to controller 103.

At step 206, controller 103 may process the voltage signal and determineif the voltage signal corresponds to a stimulus (e.g., voice command)for transitioning mobile device 102 from a low-power state to ahigher-power state. If the voltage signal corresponds to a stimulus fortransitioning mobile device 102 from a low-power state to a higher-powerstate, method 200 may proceed to step 208. Otherwise, method 200 mayproceed again to step 204.

At step 208, responsive to determining that the voltage signalcorresponds to a stimulus for transitioning mobile device 102 from alow-power state to a higher-power state, controller 103 may activate thehigher-power state by activating one or more components of mobile device102 that may have been deactivated in the low-power state (e.g.,capacitive microphone 106, user interface 105). After completion of step208, method 200 may end.

Although FIG. 2 discloses a particular number of steps to be taken withrespect to method 200, method 200 may be executed with greater or fewersteps than those depicted in FIG. 2. In addition, although FIG. 2discloses a certain order of steps to be taken with respect to method200, the steps comprising method 200 may be completed in any suitableorder.

Method 200 may be implemented using mobile device 102 or any othersystem operable to implement method 200. In certain embodiments, method200 may be implemented partially or fully in software and/or firmwareembodied in computer-readable media (e.g., memory 104) and executable bya controller (e.g., controller 103).

FIG. 3 illustrates a flow chart of an example method 300 for using aspeaker 110 as a microphone at higher volume levels not suitable forreception by capacitive microphone 106, in accordance with embodimentsof the present disclosure. According to one embodiment, method 300begins at step 302. As noted above, teachings of the present disclosureare implemented in a variety of configurations of mobile device 102. Assuch, the preferred initialization point for method 300 and the order ofthe steps comprising method 300 may depend on the implementation chosen.

At step 302, a speaker 110 may, responsive to sound incident uponspeaker 110, transmit a first voltage signal induced in the speaker 110by incident sound to controller 103. At step 304, a capacitivemicrophone 106 may, responsive to sound incident upon capacitivemicrophone 106, transmit a second voltage signal induced in capacitivemicrophone 106 by incident sound to controller 103.

At step 306, controller 103 may perform frequency equalization on thefirst voltage signal and the second voltage signal in order to accountfor differences in the frequency responses for sound received at thespeaker 110 and capacitive microphone 106. Such frequency equalizationmay be accomplished using filters (e.g., a filter bank) as is known inthe art. In particular embodiments, such filtering and frequencyequalization may be adaptive, with an adaptive filtering algorithmperformed by controller 103 during periods of time in which bothcapacitive microphone 106 is active (but not overloaded by the incidentvolume of sound) and a speaker 110 is used as a microphone. Once thefrequency response is equalized, controller 103 may smoothly transitionbetween the signals received from capacitive microphone 106 and speaker110 by cross-fading between the two. After completion of step 306,method 300 may end.

Although FIG. 3 discloses a particular number of steps to be taken withrespect to method 300, method 300 may be executed with greater or fewersteps than those depicted in FIG. 3. In addition, although FIG. 3discloses a certain order of steps to be taken with respect to method300, the steps comprising method 300 may be completed in any suitableorder.

Method 300 may be implemented using mobile device 102 or any othersystem operable to implement method 300. In certain embodiments, method300 may be implemented partially or fully in software and/or firmwareembodied in computer-readable media (e.g., memory 104) and executable bya controller (e.g., controller 103).

Methods similar to that shown in FIG. 3 may also be used for employing aspeaker 110 as a microphone at frequency ranges (e.g., low-frequencyranges) not suitable for reception by capacitive microphone 106, asdescribed above.

FIG. 4 illustrates a flow chart of an example method 400 forsimultaneously using a speaker 110 as a speaker and a microphone suchthat the speaker 110 may simultaneously emit sound while capturingsound, in accordance with embodiments of the present disclosure.According to one embodiment, method 400 begins at step 402. As notedabove, teachings of the present disclosure are implemented in a varietyof configurations of mobile device 102. As such, the preferredinitialization point for method 400 and the order of the stepscomprising method 400 may depend on the implementation chosen.

At step 402, controller 103 may determine a total voltage present on avoice coil of a speaker 110. Such voltage may include the sum of twoindividual voltages: a first voltage transmitted (e.g., by controller103) for generating sound from the speaker 110 and a second voltageinduced by external sound incident on the speaker 110.

At step 404, controller 103 may subtract the first voltage (attributableto generating sound) from the total voltage present on the voice coil,with the remaining voltage being approximately equal to the secondvoltage induced by external sound incident on the speaker 110.

At step 406, controller 103 may process the second voltage in order toperform any suitable functionality responsive to such second voltage.After completion of step 406, method 400 may end.

Although FIG. 4 discloses a particular number of steps to be taken withrespect to method 400, method 400 may be executed with greater or fewersteps than those depicted in FIG. 4. In addition, although FIG. 4discloses a certain order of steps to be taken with respect to method400, the steps comprising method 400 may be completed in any suitableorder.

Method 400 may be implemented using mobile device 102 or any othersystem operable to implement method 400. In certain embodiments, method400 may be implemented partially or fully in software and/or firmwareembodied in computer-readable media (e.g., memory 104) and executable bya controller (e.g., controller 103).

FIG. 5 illustrates a flow chart of an example method 500 for selectivelyenabling speakers 110 for transmitting sound or receiving sound, inaccordance with embodiments of the present disclosure. According to oneembodiment, method 500 begins at step 502. As noted above, teachings ofthe present disclosure are implemented in a variety of configurations ofmobile device 102. As such, the preferred initialization point formethod 500 and the order of the steps comprising method 500 may dependon the implementation chosen.

At step 502, one or more speakers 110 may, responsive to sound incidentupon speakers 110, transmit a voltage signal induced in the speakers 110by incident sound to controller 103. At step 504, controller 103 mayprocess the voltage signal to determine a volume level and/or frequencyof the incident sound.

At step 506, controller 103 may enable one or more speakers 110 totransmit sound (e.g., be used as a speaker) based on the determinedvolume level and/or frequency of the incident sound. At step 508,controller 103 may enable one or more speakers 110 to receive sound(e.g., be used as a microphone) based on the determined volume leveland/or frequency of the incident sound. After completion of step 508,method 500 may end.

Although FIG. 5 discloses a particular number of steps to be taken withrespect to method 500, method 500 may be executed with greater or fewersteps than those depicted in FIG. 5. In addition, although FIG. 5discloses a certain order of steps to be taken with respect to method500, the steps comprising method 500 may be completed in any suitableorder.

Method 500 may be implemented using mobile device 102 or any othersystem operable to implement method 500. In certain embodiments, method500 may be implemented partially or fully in software and/or firmwareembodied in computer-readable media (e.g., memory 104) and executable bya controller (e.g., controller 103).

This disclosure encompasses all changes, substitutions, variations,alterations, and modifications to the example embodiments herein that aperson having ordinary skill in the art would comprehend. Similarly,where appropriate, the appended claims encompass all changes,substitutions, variations, alterations, and modifications to the exampleembodiments herein that a person having ordinary skill in the art wouldcomprehend. Moreover, reference in the appended claims to an apparatusor system or a component of an apparatus or system being adapted to,arranged to, capable of, configured to, enabled to, operable to, oroperative to perform a particular function encompasses that apparatus,system, or component, whether or not it or that particular function isactivated, turned on, or unlocked, as long as that apparatus, system, orcomponent is so adapted, arranged, capable, configured, enabled,operable, or operative.

All examples and conditional language recited herein are intended forpedagogical objects to aid the reader in understanding the invention andthe concepts contributed by the inventor to furthering the art, and areconstrued as being without limitation to such specifically recitedexamples and conditions. Although embodiments of the present inventionshave been described in detail, it should be understood that variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the disclosure.

What is claimed is:
 1. A device comprising: a speaker for generatingsound; a capacitive microphone configured to generate a second signalinduced by sound incident on the capacitive microphone; and acontroller, communicatively coupled to the speaker, and configured to:receive a first signal from the speaker, the first signal induced atleast in part by sound incident on the speaker other than soundgenerated by the speaker; receive the second signal from the capacitivemicrophone, the second signal induced by sound incident on thecapacitive microphone; and process at least one of the first signal andthe second signal to determine at least one characteristic of soundincident upon at least one of the speaker and the capacitive microphone,wherein the at least one characteristic comprises a frequency; andselect one of the capacitive microphone and the speaker as a signalsource for incident sound based on the characteristic.
 2. The device ofclaim 1, wherein the first signal is a voltage signal.
 3. The device ofclaim 1, wherein the controller is further configured to: operate thespeaker in a first mode wherein the controller communicates an outputsignal to the speaker for generating sound; and operate the speaker in asecond mode wherein the controller deactivates the speaker from emittingsound and receives the first signal induced by sound incident on thespeaker other than sound generated by the speaker and processes thesignal.
 4. The device of claim 1, wherein the controller is furtherconfigured to transition the device from a low-power state to ahigh-power state responsive to a determination that the first signalinduced by sound incident on the speaker corresponds to stimulus fortransitioning the device from a low-power state to a high-power state.5. The device of claim 1, wherein the controller is further configuredto perform frequency equalization on the first signal and the secondsignal in order to account for differences in the frequency responses tosound incident upon the speaker and the capacitive microphone, whereinperforming frequency equalization on the first signal and the secondsignal comprises applying adaptive filtering during periods of time inwhich both the capacitive microphone is communicating the second signalto the controller and the speaker is communicating the first signal tothe controller.
 6. The device of claim 1, wherein the at least onecharacteristic comprises a sound level.
 7. The device of claim 1,wherein the controller is configured to: determine a magnitude of thefirst signal; and subtract a magnitude of a second signal from themagnitude of the first signal, the second signal communicated by thecontroller to the speaker for generating sound at the speaker, such thata difference between the magnitude of the first signal and the magnitudeof the second signal is approximately equal to a portion of the firstsignal attributable to sound incident on the speaker other than soundgenerated by the speaker.
 8. The device of claim 1, wherein thecontroller is further configured to, based on sound incident at thespeaker and sound incident on the capacitive microphone, performbeamforming to determine spatial selectivity of sounds incident on thedevice.
 9. The device of claim 1, wherein the speaker is a dynamicspeaker.
 10. A method comprising: generating, by a speaker, a firstsignal, the first signal induced at least in part by sound incident onthe speaker other than sound generated by the speaker; receiving asecond signal from a capacitive microphone, the second signal induced bysound incident on the capacitive microphone; and processing at least oneof the first signal and the second signal to determine at least onecharacteristic of sound incident upon at least one of the speaker andthe capacitive microphone, wherein the at least one characteristiccomprises a frequency; and selecting one of the capacitive microphoneand the speaker as a signal source for incident sound based on thecharacteristic.
 11. The method of claim 10, wherein the first signal isa voltage signal.
 12. The method of claim 10, further comprising:operating the speaker in a first mode wherein a controller within theenclosure communicates an output signal to the speaker for generatingsound; and operating the speaker in a second mode wherein the controllerdeactivates the speaker from emitting sound and receives the firstsignal induced by sound incident on the speaker other than soundgenerated by the speaker and processes the first signal.
 13. The methodof claim 10, further comprising transitioning a device comprising thespeaker from a low-power state to a high-power state responsive to adetermination that the first signal induced by sound incident on thespeaker corresponds to stimulus for transitioning the device from alow-power state to a high-power state.
 14. The method of claim 10,further comprising performing frequency equalization on the first signaland the second signal in order to account for differences in thefrequency responses to sound incident upon the speaker and thecapacitive microphone, wherein performing frequency equalization on thefirst signal and the second signal comprises applying adaptive filteringduring periods of time in which both the capacitive microphone iscommunicating the second signal to the controller and the speaker iscommunicating the first signal to the controller.
 15. The method ofclaim 10, wherein the at least one characteristic comprises a soundlevel.
 16. The method of claim 10, wherein processing the first signalcomprises: determining a magnitude of the first signal; and subtractinga magnitude of a second signal from the magnitude of the first signal,the second signal communicated to the speaker for generating sound atthe speaker, such that a difference between the magnitude of the firstsignal and the magnitude of the second signal is approximately equal toa portion of the first signal attributable to sound incident on thespeaker other than sound generated by the speaker.
 17. The method ofclaim 10, further comprising: based on sound incident at the speaker andsound incident on the capacitive microphone, performing beamforming todetermine spatial selectivity of sounds incident on the mobile device.18. The method of claim 10, wherein the speaker is a dynamic speaker.19. A device comprising: a first speaker for generating sound; a secondspeaker for generating sound; and a controller, communicatively coupledto the first speaker and the second speaker, and configured to: receivea first signal from the first speaker, the first signal induced at leastin part by sound incident on the first speaker other than soundgenerated by the first speaker; receive a second signal from the firstspeaker, the second signal induced at least in part by sound incident onthe second speaker other than sound generated by the second speaker;process at least one of the first signal and the second signal todetermine at least one characteristic of sound incident on at least oneof the first speaker and the second speaker; select one of the firstspeaker and the second speaker as a signal source for incident soundbased on the at least one characteristic; and select the other one ofthe first speaker and the second speaker to generate sound based on theat least one characteristic.
 20. The device of claim 19, wherein the atleast one characteristic comprises at least one of a volume level ofsound incident on the device and a frequency of sound incident on thedevice.
 21. A method comprising: generating, by a first speaker, a firstsignal, the first signal induced at least in part by sound incident onthe first speaker other than sound generated by the first speaker;generating, by a second speaker, a second signal, the second signalinduced at least in part by sound incident on the second speaker otherthan sound generated by the second speaker; processing at least one ofthe first signal and the second signal to determine at least onecharacteristic of sound incident on at least one of the first speakerand the second speaker; selecting one of the first speaker and thesecond speaker as a signal source for incident sound based on the atleast one characteristic; and selecting the other one of the firstspeaker and the second speaker to generate sound based on the at leastone characteristic.
 22. The method of claim 21, wherein the at least onecharacteristic comprises at least one of a volume level of soundincident on at least one of the first speaker and the second speaker anda frequency of sound incident on at least one of the first speaker andthe second speaker.